The present invention relates generally to agricultural machinery and, more particularly, to improvements to hay making machines having a plurality of working elements.
The working elements in hay making machines of this type are in the form of rotary rakes which rotate about generally vertical axes and are arranged on mutually articulated intermediate frames. These frames can be pivoted relative to one another about axes extending in the direction of travel. The intermediate frames supporting the rotary rakes can thereby be pivoted from a working position into a transportation position and vice versa. Moreover, the working elements are supported by means of land wheels. Each working element, independently of the other working elements, can follow any unevenness in the ground being traversed by its respective wheel.
A shaft-coupling consisting of relatively pivotal coupling units is known from French patent specification FR 1 251 794. One coupling unit comprises finger-like meshing elements arranged horizontally around a circle, the interstices of the fingers being occupied by radially outwardly extending meshing elements on the other coupling unit. In this arrangement, the axes of the meshing elements are mutually perpendicular. Each of the coupling units is rigidly attached to a respective end of the shafts that are connected by means of this coupling arrangement. In the opening direction of the coupling, constructional constraints limit the angle through which such a coupling can pivot, however it may be considerably greater than 180.degree.. By contrast, the movement in the closing direction of the coupling ceases when the flanges supporting the meshing elements of the two coupling units rest upon one another. Thus, if used in a hay making machine of the type described above, this coupling arrangement would be unable to produce a so-called negative pivotal angle, as is required when a land wheel sinks into a depression in the ground. This deficiency is overcome in European patent specification EP 370 933 by providing each of the coupling units with very long finger-like meshing elements that are disposed around respective circles whereby the axes of the finger-like meshing elements of the two coupling units will extend in parallel with one another when the coupling is closed. A coupling constructed in this manner is capable of providing negative pivotal angles when there are depressions in the ground. However, the finger-like meshing elements in the two coupling units are subjected to very high loads because they can only make contact at their front ends if a collision with the respective flange of the other coupling unit is to be avoided. Highly stressed zones, which could lead to bending or even breakage of the finger-like meshing elements, may be formed at the opposite ends thereof where they merge into their respective coupling flanges. To avoid such damage including, hardening of the finger-like meshing elements, EP 370 933 proposes to make the cross-section of the finger-like meshing elements less susceptible to loads by adopting a shape that differs from the easily manufactured cylindrical one. EP 370 933 further proposes to attach the meshing elements to the flange of the respective coupling unit in a detachable manner. However, the problem of high loads on the long finger-like meshing elements is not overcome by these measures, which of course increase the cost of the coupling.
It is an object of the present invention to overcome one or more of the above described deficiencies.
Another object of the invention is to provide a simply constructed hay making machine such that a short, space-saving coupling can be arranged in the drive train between the relatively moveable working elements, thereby allowing ground-following movement of each working element and pivoting thereof from a working position into a transportation position and vice versa.
A further object is to provide an arrangement whereby the meshing elements of the coupling units forming the coupling will be subjected to very low loads and hence will suffer much lower wear-and-tear compared to the state of the art.